Yes, Roam has spent a few nights at Indian casinos. I've seen a guide book on RV parking at casinos, but can't quote the title or author.
The Kewadin Casino in St. Ignace, Michigan has a nice park. It costs $20/night, but you get two nights free if you join their loyalty club at no cost. The meals and entertainment are bargains on weekdays. Cheryll puts a few dollars in the slots, and I don't gamble. They haven't hit me with much in the way of mailings or spam as a result of our membership.
On our return trip from Anacortes to Michigan earlier this month, we also stopped at the Winnevegas Casino in Sloan, Iowa. It's free to park in the asphalt lot. Electricity is available for $11/night. They also sell cheap diesel and gasoline. It seems that they aren't subject to the same fuel taxes on tribal lands. I don't understand how it all works, but buying fuel there probably puts a crimp in the state and/or federal highway funds.
We've also stopped at a couple of Walmarts, but found them to be rather noisy, and after a long day on the road, I get tired of answering the usual questions from non-boaters about a tugboat in a Walmart parking lot. I'd rather pay $20-30 for a campground that's set at least a half mile from the freeway. We still get the looks, stares and a few questions, but it's a lot more peaceful and we get showers and better bathrooms.
Of course, if there's a storm in the forecast, or it's too hot to sleep, we stay in a hotel. We can usually find one from the coupon books that are free at rest stops and information centers. The discounted rates are usually only good for walk-ins, but we always call in advance. Our first question is; "Do you have room to park a pickup truck with a 32-foot trailer?"
Rich